A curious pattern was noted by the author with regards to ich. The author did a survey of fish hobbyists. Some 70 hobbyists related that they had never had a fish die from ich. Only three reported they had fish die (all appeared to be “newbies” setting up new aquariums with new filters and doing fish-in cycling). Yet in some thirty research papers on treating ich virtually all had sets of data with 100% fish deaths due to ich.
Examination showed one common thread, all the research papers used aquariums or containers without filtration. The hobbyists probably all had filtration on their aquariums. So the vast majority of the fish without filtration in an aquarium die and the vast majority of fish with filtration in an aquarium live. The conclusion is rather obvious. Filtration is important for treating ich. The mechanism by which this works is actually quite simple. Below in the “discussion” portion of this article we show the cause and effect for this relationship.
As a result of this mechanism one should never turn off the filter when treating ich and one should never change out or clean the filter media. Just leave the brown gunk to filter out the ich theronts. And never transfer the sick fish to a hospital tank that does not have a mature filter on it. Leave them in the tank with the most established filter.
One Facebook commentator had ich pop up. He set up an “emergency” hospital tank with a new filter and put the infected fish into it. He took the temperature up. All the fish died. Not a good idea! The lack of microscopic carnivores in the new filter, coupled with using an ineffective medication, let ich kill the fish.
This is an actual comment from Facebook:
“We also got Ick from PetSmart 2 weeks ago, went through the whole process. Used Melafix per the PetSmart expert. Canister filter had to be shut down cleaned. All is well now, we only lost 2 fish.”
If this hobbyist had not cleaned their canister they probably would not have lost any fish. If the hobbyist had used a good medication like Ich X they also would not have lost any fish (Melafix is as useless as teats on a boar hog).
Another Facebook commentator asked:
“I set up a new tank per the instructions of my LFS and added Prime, StressGuard and Stability. Per the instructions of my LFS I added four platies, six neons, and two angelfish. They all got white spot disease. So I added Metroplex per the instructions. All my fish died. Where did I go wrong?“
Again, the lack of microscopic carnivores in a new filter coupled with an ineffective medication doomed the fish. Note this will always be blamed by the experts on “ammonia poisoning” or “new tank syndrome”. This is one of the main reasons I do not recommend fish-in cycling. With fish-in cycling there is no brown gunk in the filter which will remove the ich theront. So if ich pops up, the fish will die unless one uses a good medication like ich X.
Another thing to think about in ich and indeed in all fish diseases is the filtration efficiency of the aquarium. Ich has an infectious stage, a tiny free-swimming ciliate (a theront) which swims in the water columns trying to find a fish to infect. This infectious stage is 50 to 100 microns in size. Let say for illustration a fish just added to a 50-gallon aquarium has a latent (or dormant) ich cyst which decides to become active because the fish has been overstressed in the pet store.
The ich cyst falls off the fish, attaches to a plant or the substrate, and produces up to 1000 free swimming infectious stages (theronts). Let say 99% of the infectious stages die before they find a fish but that leaves 10 infectious stages which find a fish. These 10 infectious stages are more than enough to start an epidemic in the aquarium. The progression is 10 – 100 – 1,000 – 10,000. Somewhere between 1,000 and 10,000 the aquarium owner will realize they have a problem. So what does filtration do?
To answer that question let us assume you have an undergravel filter powered by two powerheads in a 50-gallon aquarium. Each powerhead has a flow of 145 gallons per hour. That’s about six water changes per hour going through the gravel.
The gravel (which in this case is the filter media) has a mulm in it, a brown detritus from months of operation. This mulm is not protein filled waste bleeding ammonia into the aquarium as some would have you believe. This mulm is a small microscopic community. This community typically includes a surprising number of protozoan carnivores 50 to 500 microns in size. These carnivores include stentors, rotifers, ciliates, flagellates, paramecium, etc.
The mulm is full of small passages through which the water swirls. As the ich infectious stage infected water goes through these passages two things happen. First the infectious stages stick to the mucilaginous surface of the mulm where they typically die. Secondly the infectious stages are captured and eaten by the microscopic carnivores.
In a well established aquarium the water is pretty free of small organisms that feed the microscopic carnivores in the filter “gunk”. So initially there are not a lot of microscopic carnivores in the filter. So initially the ich organism multiplies rapidly and all the fish become covered with ich spots. But the ich theronts released in this first wave of the ich pathogen feed an explosion in the population of the microscopic carnivores.
So the second wave of theronts released by the ich tomonts in the substrate are set upon by a huge population of microscopic carnivores and literally eaten as they pass through a well established filter.
Let’s say 95% of the infectious stages in the second “wave” of ich passing through the gravel survive the journey. Because the water is turning over rapidly through the gravel the ich theront has to make this perilous journey 144 times in 24 hours. This means only 2% of the infectious theronts from the second wave will have survived the gravel. In our example of ten infectious theronts stages surviving, none of them would have survived the journey through the gravel 144 times and would not be able to infect a fish and continue the cycle.
This is probably the main mechanism which controls ich in the aquarium. While research studies showing this mechanism with regard to ich are lacking, one study did find this filtration control relationship for flukes:
“Epidemiology of Pseudodactylogyrosis in an Intensive Eel-culture System”, Kurt Buchmann, 1988
“Settling of oncomiracida was negatively correlated to activity of free-living organisms in the biofilm on the fish tank wall. Laboratory tests showed that the biofilm-organism Stenostomum sp. (Turbellaria) ingested Pseudodactylogyrus eggs. It is suggested that predatory activity of biofilm organisms influences the infection level.”
This analysis is not limited to under-gravel filtration. All biofilters will do this to some degree. Uncleaned sponge (open celled urethane foam) will be especially good at this task due to its morphology. The larger the volume and the surface area of the filtration media, the better it will be at removing disease organisms.
Note that many people in “old times” successfully used the Vortex (model XL 400 GPH) diatomaceous earth (DE) filter to treat ich and other disease. DE filters can remove many free-swimming infective stages of various parasites from the aquarium water before they can attach to their hosts, and when the attached adult parasites on the fish die, the fish are eventually left parasite-free. These filters just mechanically filtered out the theronts.
A UV lamp set up would also kill the theront. Because of the Reciprocity Rule in Photobiology, an ich theront is easily killed by even a small UV unit. Note this is contrary to what all the “experts” say. See the section on UV to get a clearer picture of this.
Ich in more Depth
Ich is the most common fish disease and warrants a more in-depth discussion. The following chapters are devoted to this common fish disease:
Aquarium Science Website
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